1. Field of the Disclosure
This invention provides glucagon superfamily peptides conjugated to nuclear hormone receptor ligands that are capable of acting at nuclear hormone receptors.
2. Brief Description of Related Technology
Nuclear hormone receptor proteins form a class of ligand activated proteins that, when bound to specific sequences of DNA, serve as on-off switches for transcription within the cell nucleus. These switches control the development and differentiation of skin, bone and behavioral centers in the brain, as well as the continual regulation of reproductive tissues.
Nuclear hormone receptor ligands such as steroids, sterols, retinoids, thyroid hormones, and vitamin D function to activate nuclear hormone receptors. The interaction of the hormone and receptor triggers a conformational change in the receptor, which results in the up-regulation of gene expression. The level of cellular signal transduction activated by the interaction of a ligand and a nuclear hormone receptor is determined by the number of ligands and receptors available for binding, and by the binding affinity between the ligand and the receptor. Many ligands and corresponding analogs that bind to nuclear hormone receptors are used as medication to treat, for example, Parkinson's disease (NURR1), sleep disorders (RZRβ), arthritis and cerebellar ataxia (RORu), central nervous system disorders (NOR-1, Rev-ErbAβ, T1x, NGFI-Bβ, HZF-2α, COUP-TFα, COUP-TFβ, COUR-TFγ, NUR77), hypercholesterolemia (LXRα, COR), obesity (Rev-ErbAα), diabetes (HNF4α), immune disorders (TOR), metabolic disorders (MB67α, SHP, FXR, SF-1, LXRβ), and infertility and contraception (GCNF, TR2-11α,β, TR4, ERα,β ERRα,β).
Pre-proglucagon is a 158 amino acid precursor polypeptide that is processed in different tissues to form a number of different proglucagon-derived peptides, including glucagon, glucagon-like peptide-1 (GLP-1), glucagon-like peptide-2 (GLP-2) and oxyntomodulin (OXM), that are involved in a wide variety of physiological functions, including glucose homeostasis, insulin secretion, gastric emptying, and intestinal growth, as well as the regulation of food intake. Glucagon is a 29-amino acid peptide that corresponds to amino acids 33 through 61 of pre-proglucagon, while GLP-1 is produced as a 37-amino acid peptide that corresponds to amino acids 72 through 108 of pre-proglucagon. GLP-1(7-36) amide or GLP-1(7-37) acid are biologically potent forms of GLP-1, that demonstrate essentially equivalent activity at the GLP-1 receptor.
Glucagon is used in the acute treatment of severe hypoglycemia. Oxyntomodulin has been reported to have pharmacological ability to suppress appetite and lower body weight. GLP-1 and GLP-1 receptor agonists are used as treatment for Type II diabetes. Exendin-4 is a peptide present in the saliva of the Gila monster that resembles GLP-1 in structure, and like glucagon and GLP-1, increases insulin release.
Gastric inhibitory polypeptide (GIP) is also known as a glucose-dependent insulinotropic peptide, and is a member of the secretin family of hormones. GIP is derived from a 153-amino acid proprotein encoded by the GIP gene and circulates as a biologically active 42-amino acid peptide. The GIP gene is expressed in the small intestine as well as the salivary glands and is a weak inhibitor of gastric acid secretion. In addition to its inhibitory effects in the stomach, in the presence of glucose, GIP enhances insulin release by pancreatic beta islet cells when administered in physiological doses. GIP is believed to function as an enteric factor that stimulates the release of pancreatic insulin and that may play a physiological role in maintaining glucose homeostasis.
Osteocalcin is a noncollagenous protein found in bone and dentin. It is secreted by osteoblasts and thought to play a role in mineralization and calcium ion homeostasis. Osteocalcin has also been reported to function as a hormone in the body, causing beta cells in the pancreas to release more insulin, and at the same time directing fat cells to release the hormone adiponectin, which increases sensitivity to insulin.